Radio relaying



Feb. 10, 1942. H, Tumck 2,272,312

RADIO RELAYING Filed May 20, 1939 4 Shets-Sheet 1 INV EN TOR.

yaw TUNICK 776? W A TTORN E Y.

Feb. 10,, 1942. T K 2,272,312

RADIO RELAYING Filed May 20, 1939 4 Sheets-Sheet 2 METAL W 3 REFLECTOR R5 F] METAL 50X CONTAIN/N6 5;; V /'$H/ELDED AMPLIFIER RSA rRANsM/rr/ 6\ANTENNA p5p y5 A TRANSMITTING 0R RECEIVING ANTENNA maNsMlr- \jITRANSM/TMETAL $UPPORT RECEIVE REFLECTOR METAL REFLECTOR METAL METAL SUPPORTSHIELD FOR REFLECTOR INVENTOR. H 12/2) TUN/CK BY ATTORNEY.

' Feb, 10, 1942. H. TUINICK 2,272,312

RADIO REIQAYING Filed May 20, 1939 4 Sheets-Sheet s INVENTOR. :ZRRYTU/v/CK A TTORN E Y Patented Feb. 10, 1942 RADIO Harry Tunick, Rye, N.Y.,. ass'ignor to RadioCorporation of America, a cor'pbration ofDelaware Application May 20, 1939. Serial N6. 274,744

3 Claims. (Cl. 250-15) My present invention relates to radio relaying.For some types of service and also in order to conserve channelfrequencies, it is desirable when relaying radio signals from one pointto another to retransmit on the same frequency as that received. Atradio relaying stations, because of the close proximity of the receivingand transmitting antennas, some of the energy radiated from thetransmitting antenna leaks back into the receiving antenna, therebysetting up sustained oscillations at the relaying point. To overcomethis difiiculty is the principal object of'my present invention.

Turning to the accompanying drawings, which illustrates various ways inwhich the main object of my present invention may be effected:

Figure 1 illustrates a radio relaying system in which a conductivescreen is employed to prevent interaction between the receiving andtransmit-,

ting antennas;

Figure 2 is a modification of Figure I;

Figure 3 illustrates a modification in which undesirable interaction isavoided by using antennas of different polarization at the relayingstation;

Figure 3A is a structural modification of Figure 3 Figure 4 is amodification of Figure 3;

Figure 4A is a modification of Figure 4 in which terminated rhombicantennas arranged in difierent planes of polarization are employed atthe relaying station;

Figure 5 is a still further modification in which the feedback of theaerial path is neutralized;

Figure 6 illustrates a form of my invention in which the tendencytowards oscillation generation is reduced by virtue of an adjustabletransmission line;

Figure 7 illustrates still another modification of my invention;

Figure 7a illustrates one form of intensity and phase adjustor which maybe used in the organization shown in Figure 7, while Figure 7b shows afurther modification of a portion of Figure 7.

Turning to Figure 1, waves received upon a receiving antenna RA at arelay station are amplified in a relay station amplifier RSA andretransmitted at .the same frequency over a transmitting antenna TA. Theentire system is preferably mounted upon a high support, such as a poleor a tower P or tall building. Preferably in my system, ultra shortwaves are employed of the order of magnitude of less than ten metersdown to a fraction of a meter. The

antennas RA and TA are of the type such as described by P. S. Carter inU. S. Patent No. 1,974,387 or by N. E. Lindenblad in U. S. Patent 'No.1,927,522, or they may be of the types described by Carter, Lindenbladand Hansell in the Proceedings-of the Institute of Radio Engineers forOctober 1931. It is to beunderstood that the receiving and transmittingantennas may be of these types in any of Figures 1 to 7 or a combinationof these types, or they may be of the type described by Bruce; BeckandLowry in the Proceedings of the Institute of Radio Engineers forJanuary 1935.

Because of the close proximity of the'transmitting antenna TA to thereceiving antenna RA, especially when retransmitting at the samefrequency as the frequency of the waves received upon receiving antennaRA,'it will be found that there is a tendency for oscillationgeneration. This is due to the fact that some of the energy radiatedfrom the transmitting antenna TAjleaks back into the input circuit ofthe amplifier RSA through the receiving antenna RA. To avoid thisdiificulty I interpose between the transmittingYantenna and receivingantenna a large metallic shield MS which may be made in the form of ametallic billboard suitably perforated so that various leads in theamplifier RSA may pass therethrough. The shield MS is grounded by directconnection to the metallic tower P. As an alternative, a heavyconnection in the form of an adjustable transmission line may beemployed so that the shield MS by virtue of adjusting the trombone slideTS is maintained at ground radio frequency potential.

A variable capacitive reactance 26 may be con- ;nected to the tower Pand shielding screen MS so that the tower itself series resonates withthe screen MS at the operating carrier frequency, in-

suring complete grounding of the screen MS in spite of the unavoidableimpedance to the operating frequencies presented by the tower P.

In the modification shown in Figure; 2, the grounded metallic shield isdiagrammatically indicated at MS and the relaying-station amplifier isindicated by BSA. The receiving antenna in thisca'sahowever, is in theform of. a receiving dipole RD and the transmitting antenna is in theform of a transmitting dipole TD. Further shielding is provided by meansof the receiving parabolic reflector RPR and the transmitting parabolicreflector TPR. The parabolic reflectors may be made of continuous smoothmetallic surfaces or they may be made up'in the form of wires. Also, themetallic reflectors may be cylindrical parabolas rather than theparaboloid structures illustrated.

In Figure 3 the receiving antenna RA is shown as a dipole of thevertically polarized type and the transmitting antenna TA is arranged soas to be horizontally polarized. In this way, coupling between the twoantennas is reduced. To further reduce coupling, the grounded metallicshield MS, as before, may be employed.

In connection with Figure 3 the system may be modified as shown inFigure 3a, in which case the receiving station amplifier RSA" is mountedwithin the metallic compartments RSA which also house the two antennas,as shown. That is, the receiving station amplifier housings RSA and RSAare made of metal and serve as a screen for the amplifyin'gapparatuswithin, and also as reflectors for the vertically polarized receivingantenna RA and for the horizontally polarized transmitting antenna TA.

Figure 4 is similar to Figure 3 with the exception that the transmittingand receiving antennas are of the V type such as described by Carter andLindenblad referred to hereinabove. In either Figure 3 or 4 it should beunderstood, of course, that the receiving antenna may be horizontallypolarized and the transmitting antenna vertically polarized, or theantennas may be of any polarization provided the electrical vectors orfields emitted and received by the antennae, respectively, are at rightangles to each other. As a further modification, the receiving antennaRA of Figure 4 may be of the rhombic type, as illustrated in Figure 4A,and the transmitting antenna may also be of the rhombic type, eachantenna being terminated with a surge resistance SR. As before, theplanes of the antennae should be at right angles to each other to reducecross-coupling and a grounded metallic shield receiving antenna from therelay station transmitting antenna TA is efiectively reduced by thereceiving antenna surge resistance SR before it is reflected back intothe relay station amplifier RSA.

In the modification shown in Figure 5 the re-:

ceiving antenna RA and transmitting antenna TA are coupled togetherthrough transmission lines TLI and 'I'LZ. Connected in the transmissionlines there is a phase and intensity adjusting device PA. By adjustingthe phase and intensityrgjs adjusting device PA, the energy picked up bythe relay station receiving antenna from the relay station transmittingantenna may be completely balanced out. If desired, shielding may alsobe employed in connection with the system of Fig-=5: ure 5 in the formof the grounded metallic shield I The feedback velocity through thetransmission lines TLI and TL2 and phase adjuster PAI is necessarilyslower than the feedback velocity" ifications, the shield MS isrelatively large with respect to the physical dimensions of the antennaeemployed at the relaying station.

In the system shown in Figure 6, the shield MS may be employed asbefore. In the arrangement of Figure 6, however, the transmission lineTL leading to the transmitting antenna TA is made adjustable in lengthby means of trombone slides TS! and TSZ. For oscillation generation, itis essential that the feedback path maintain a degree phase relationshipbetween the input and output circuits here represented by thetransmitting antenna TA and receiving antenna RA. This relationship maybe spoiled for oscillation generation by the use of the sliders TSI andTS2 which should be adjusted so that the tendency towards oscillationgeneration is reduced or eliminated. As before, the grounded metallicshield MS may be employed. In order to efiectively ground the metallicshield, tuning means, illustrated in the form of variable inductances Land variable capacities C, may be used. These inductors and capacitorsare adjusted so as to series resonate at the frequency employed wherebythe shield, connected to one extreme of the series tuned circuits, is atground potential, since the other extreme of the series tuned circuit isconnected to ground.

The two wire transmission lines, such as TL of Figure 6 for example,should be short, say a few wavelengths or within a fraction of awavelength long in order to reduce losses. Since the receiving antennaRA carries only a very small current, the transmission line TL betweenthe receiving antenna and the relay station amplifier RSA may be madeseveral wavelengths long since the further apart the receiving andtransmitting antennas are, the less will be the reaction between them.In this respect, the receiving antenna may be mounted some distance downon the supporting tower P and the transmitting antenna may be at thehighest elevation on the tower. .Both the transmission lines leading tothe receiving and transmitting antennae of any of the relay stationsillustrated may be placed within grounded metallic tubes to preventstray radiation and pick-up. If desired, the transmission line to thetransmitting antenna may be of the open two wire type and the line tothe receiving antenna may be of the concentric conductor type, or viceversa, or both transmission lines may be of the concentric conductortype or, as illustrated, of the two conductor open wire type. In all ofthe modifications illustrated, the dipole antennae for very widefrequency band radio relaying may be constructed as ellipsoids, asdescribed in the copending application of Nils E. Lindenblad, Serial#208,573, filed May 18, 1938, now Patent #2.,239,724, granted April 29,1941.

In the modification shown in Figure 7, a correcting dipole CD mountedwithin a parabolic reflector PR is connected by way of a transmissionline TL to the input circuit of the amplifier RSA. The correcting dipoleis arranged to be polarized in the same way that the transmittingantenna TA is polarized. The receiving antenna RA may be of the samepolarization, but, preferably is polarized at right angles to antennaeTA and CD. By means of phase adjusting and intensity controlling devicePAI, the amount of energy fed from the correcting dipole into the inputside of the relay station amplifier RSA is adjusted so as to equal inamplitude and be opposite in phase to that fed by the transmittingantenna TA over leakage paths into the input side of the relay stationamplifier RSA. The parabolic reflector PR associated with the correctingdipole CD insures that the correcting dipole picks up only energyradiated by the relay station transmitting antenna and that it does notpick up any of the energy coming in from the left, namely, energy whichit is desired that the relay station retransmit.

One form of intensity and phase adjuster PAI of Figure '7 is illustratedin Figure 7A. By varying the coupling between the loops LP, theintensity of currents fed from the correcting dipole to the receivingamplifier RSA may be controlled. By adjusting the short circuitingstraps S along the line stubs LS, the phase of energy fed from thecorrecting dipole into the relay station amplifier RSA may be adjusted.If desired,

the lines stubs and short circuiting straps S may be replaced bytrombones such as are illustrated in Figure 6.

It should be clearly understood that various features shown in thevarious figures may be combined without departing from the scope of mypresent invention. Thus, referring to Figure 7 a grounded metallicshield, which may be grounded at several points, may be employed at aposition such as indicated, namely, between the receiving antenna RA andthe rear of the parabolic reflector PR of the correcting dipole CD.Naturally, th screen MS of Figure 7 is also between the receivingantenna RA and the transmitting antenna TA. Also, in Figure '7 thetransmission lines leading to both the receiving antenna RA andtransmitting antenna TA may be provided with adjustable trombone slidesTSI and TS2 as shown in Figure 7b so that their lengths may be adjustedfor optimum operation with a minimum of regeneration. The portionbetween dotted lines XX and YY of Figure 7 in either or bothtransmission lines may be substituted by the structure shown in Figure7b.

In Figure 4A the two antennae RA and TA may have their longitudinal axesin line, but the planes of the conductors of each antenna are preferablyarranged at right angles to one another. In addition, with reference toFigure 4A for example, not only may the metallic shield MS be used, butthe neutralizing circuit of Figure 5, or, for that matter, thecorrecting antenna pick-up system of Figure 7, may be employed. In thelatter event, it may be found unnecessary to employ the shield MS ofFigure 4A.

Also, it should be understood that my invention as described hereinaboveis not limited to a relay station where retransmission takes place onthe same frequency as that received. It should be understood, therefore,that in each of the figures described hereinbefore, the receivingstation amplifier may be considered as employing demodulating apparatusfor the received waves and means for generating a new carrier frequencywhich is modulated in accordance with the received demodulated waves.The retransmission may, therefore, take place on a different frequency.Further, if desired, the received waves maybe demodulated and then usedto modulate locally generated waves of the same mean or carrierfrequency as the waves received.

Having thus described my invention, what I claim is:

1. In an ultra short wave relaying system, a relay station comprising areceiving antenna and transmitting antenna, amplifying means connectedtherebetween and a metallic shield between said antennas for preventingfeedback from said transmitting antenna to said receiving antenna, saidstation being supported a substantial distance above ground on aconductive support, said shield being connected to said support and saidsupport unavoidably presenting an impedance between said shield andground, and means for maintaining said shield at zero radio frequencypotentials with respect to ground comprising a tuned circuit connectedbetween said metallic shield and ground.

2. In an ultra short wave relaying system, a relay station, comprising areceiving antenna and transmitting antenna, amplifying means connectedtherebetween, a metallic shield between said antennas for preventingfeedback from said transmitting antenna to said receiving antenna, saidstation being supported a substantial'distance above ground on aconductive support, said shield being connected to said support and acapacitive reactance connected across at least a portion of said supportfor resonating said support to the operating frequency of said station.

3. In an ultra short wave relaying system, a relay station comprising areceiving antenna and a transmitting antenna, amplifying means connectedtherebetween and a metallic shield between said antennas for preventingfeedback from said transmitting antenna to said receiving antenna, saidstation being supported a substantial distance above ground on aconductive support, said shield being connected to said support, saidsupport presenting an impedance between said shield and ground, andmeans for maintaining said shield at ground potential at the operatingfrequency of said station comprising a variable length connectionbetween said metallic shield and ground, said connection beingadjustable to such length that both ends thereof are effectively atground radio frequency potential.

HARRY TUNICK.

